Fix PHP 8.4 deprecation warnings

[TomA-R]

Fixes warnings like:

Deprecated: Stringy\Stringy::__construct(): Implicitly marking parameter $encoding as nullable is deprecated, the explicit nullable type must be used instead in Stringy/src/Stringy.php on line 77
Deprecated: Stringy\Stringy::between(): Implicitly marking parameter $offset as nullable is deprecated, the explicit nullable type must be used instead in Stringy/src/Stringy.php on line 601
Deprecated: Stringy\Stringy::create(): Implicitly marking parameter $encoding as nullable is deprecated, the explicit nullable type must be used instead in Stringy/src/Stringy.php on line 957
Deprecated: Stringy\Stringy::extractText(): Implicitly marking parameter $length as nullable is deprecated, the explicit nullable type must be used instead in Stringy/src/Stringy.php on line 1324
Deprecated: Stringy\Stringy::lineWrap(): Implicitly marking parameter $delimiter as nullable is deprecated, the explicit nullable type must be used instead in Stringy/src/Stringy.php on line 2652
Deprecated: Stringy\Stringy::lineWrapAfterWord(): Implicitly marking parameter $delimiter as nullable is deprecated, the explicit nullable type must be used instead in Stringy/src/Stringy.php on line 2691

..and more

cc @voku for your review

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This change is 

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[JasonStainton]

+1 getting this pushed through. I've never seen so many deprecations warnings 😅

[Elnadrion]

Same here. @voku could you please consider merging it? 🙏

[Anubarak]

@voku Are there any plans to merge it in the future?